Photoelectric transmitter



April 7, 1942. M. POTTS I PHOTOELECTRIC TRANSMITTER Filed Dec. 22, 1938,-15 Sheets-Sheet-l FIG. 5

FIG. 4

INVENT OR. LOUIS M. POTTS ORNEY.

A ril 7, 1942. l P TTS 2,278,485

PHOTOELECTRIC TRANSMITTER I I Filed Dec. 22, 1938 Z Sheets-Sheet 2 FIG.2

III

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INVENTOR. LOUIS M. POTTS ATTORNEY.

mitters in each group have Patented Apr. 7, 1942 Louis M. Potts,Evanston, 111.,

type Corporation, Chicago, 111.,

of Delaware assignor to Tele-' a corporation Application December22,1938, Serial No. 247,181 32 Claims. (Cl. 178- 50) The presentinvention pertains to telegraph transmitters and particularly to atransmitter in which the transmission of signaling impulses iscontrolled through a photoelectric system.

The primary object of the invention is to control photoelectrically thetransmission of permutation code signals in a multiplex telegraphsignaling system.

Another object is to provide in a multiplex signaling system, aplurality of photoelectric transmitters, each transmitter comprising ascanning device, and each scanning device acting as a transmittingdistributor.

Another object of the invention is to provide a photoelectric signalingsystemhaving a plurality of scanning devices, and means within thesystem to maintains. predetermined phase relation between the scanningdevices.

Another object is to provide in a multiplex si naling system, aplurality of photoelectric scanning devices, means to transmit charactersignals, and means to control successive signals by different 'ones ofsaid scanning devices.

A further object of the invention is to provide in a multiplex signalingsystem, a plurality of photoelectric scanning devices driven by directconnection from a motor, and means for maintaining between said devicesa definite phase relation.

Another object of the invention is to provide a photoelectric signalingsystem having a plurality of scanning devices, wherein each scanningdevice is provided with its independent motor drive, and means withinthe system to maintain a predetermined phase relation between thescanning devices.

The system according the present invention comprises a plurality ofgroups of synchronous motors connected in series. To onemotor in eachgroup is associated a sunflower type of multiplex'distributor and toeach of the other motors of each a scanning device of the type disclosedin United States Patent 2,177,077, granted October 24, 1939, to L. M.Potts. The scanning drums of the transtheir apertures arranged so thatthe five apertures on one drum occupy one-quarter of the circumference,and the drums oi the different transmitters are so arranged that theapertures in the next trans.- mitter begin where the apertures in thepreceding transmitter end, so, if all the drums were considered as onethere would be twenty apertures. equally spaced around thecircumference. A0-

to one embodiment of I group is associated a photoelectric multiplexsystem is provided wherein all of the photoelectric transmitters aredriven by direct shaft connection from a single motor. With thisarrangement the scanning devices and circuits therefor are similar tothat of the first-mentioned embodiment; a

A feature of the system according to the present invention consists inproviding a single amplifying circuit for each group of scanners; thatis, all of the photoelectric cells in each group are connected inparalleland to a single amplifying circuit which'may be similar to theamplifier disclosed in said patent. In the plate circuit of the lasttube in the amplifying'circuitis a polarized relay having threewindings, one of which is' a biasing winding, the biasing action ofwhich is governed by one pair of the rings on the distributor. Anotherpair of rings on the distributor controls the excitation of twooperating windings of the polarized relay in such a manner that thenormal impulses in some of the channels are made positive and in othersnegative, so that when all channels are idle, reversals'will still besent ,for synchronizing, purposes, as is the usual'practice. A fourthpair of rings of the distributor serve to connect'the plate circuit ofthe last tube in the amplifying circuit toone or the other of theoperating windings of the relay, and the relay serves to transmit to theline impulses controlled by the four transmitters.

A better understanding of the invention may be had from the followingdescription, taken in conjunction with the accompanying drawings,wherein like reference-characters designate similar parts throughout theseveral views, and in which,

Fig. 1 is a diagrammatic view of the circuits and apparatus for atransmitting distributing arrangement embodying the present invention;"Fig. 2 is a cross-sectional view of the scanning device employed withthe present invention; a

Fig. 3115 a view taken on line 3-3 of the Fig. 4 is a view taken on line4-4 of Fig. 2; Fig. 5 is a view taken on'line 5-5 of Fig. 2;

Fig. 6 is a schematic view of the tape control circuit for thephotoelectric transmitters;

Fig. 7- is a perspective representation of a portion of perforated tape;

Fig; 8 is a perspective representation of a 7 portion of printed tape;

cording to another embodiment of the invention Fig. 9 is across-sectional view of a photoelectric transmitting arrangement inwhich a plurality of transmitters are driven by direct shaft connectionfrom the motor; and

Fig. is a schematic diagram of the electrical circuit employed with thearrangement shown in Pig. 9 when printed tape is used.

Having reference to Fig. 1. which is a schematic representation of aspecific embodiment of the present invention, the transmittingdistributor is indicated generally by the reference character II. Thedistributor arm I: of the transmitting distributor ll Ls secured to ashaft II of an impulse or other suitable synchronous motor l4, such asused for driving multiplex distributors, which motor is provided with asuitable damper it. A control motor I of a type known asauto-synchronous is also associated with the motor l4. Motor It may havean ordinary field winding 11, of the type in which the field has a largenumber of spaced slots and the winding equally distributed around thecircumference. The armature it of motor I. has two poles with a singlewinding is whose terminals are brought to collector rings (not shown).Three equally spaced terminals are brought out from the field winding ofthe contrd motor II. If any number of such motors II have thecorresponding field terminals connected together and the brushesconnected to the same some of alternating current, and any once! thearmatures II is moved, all of the other armatures will follow exactly.The motor I. is connected in this manner to four other similar motors22, II, 24, and It, so that the motors 2! to "will be kept in exactphase relation to motor ll. Each of the motors 22 to 25 drives aphotoelectric transmitter similar to that shown in the aforementionedpatent.

To the shaft of each of the synchronous motors 22 to II is secured ascanning cylinder 26. The scanning drums or cylinders 16 have aperturesarranged as shown in Fig. 9. It will be noted that (in a four channelmultiplex system) the five apertures 21 on one drum occupy onequarter ofthe periphery. It will also be observed that the drums or cylinders 20on the different transmitters associated with the motors 22; to 2| areso arranged that the apertures in any one of the drums or cylindersbegin where the apertures in the immediately preceding cylinder end, sothat, if all the drums or cylinders are conaidered as one unit therewould be twenty apertures 21 equally spaced around the periphery.

Positioned within the scanning cylinder or dnnn I! (Fig. 2) is aphotoelectric cell 28, which is indicated diagrammatically in Fig. 1 bya cathode 2! and an anode II. The optical system is showndiagrammatically in Fig. 1 by the incandescent lamp 3!.

Having reference to Fig. 2, there is shown a photoelectric transmittersimilar to that shown in Figs. 6 and 7 of the aforementioned patent towhich referencemay be had for a more detailed description ofthe'structure. The photoelectric transmitter illustrated in Fig.2comprises essentially an optical system or apparatus and a scanningmechanism indicated generally as 33 and 84, respectively. The baseportion of the transmitter comprises a top plate 35, a bottom plate 30and vertical post (not shown) separating said plates. From the lowersurface of top plate II is suspended the scanning arrangement 84, whichcomprises a shaft 31 iournaled in brackets ll and 39 depending from andintegral with top plate II. Clamped between nuts 4| and 42, threaded'onshaft 31 at the left extremity thereof, is a scanning cylinder or drum26. In this manner, cylinder 26 is adjustable longitudinally of shaft81, as well as angularly thereof with respect to the stop position ofthe shaft, as will hereinafter appear. The scanning cylinder 26 isprovided with a helically arranged series of slots 21 corresponding innumber to the number of code hole positions in the tape. It will beobserved that with the present structure no provision is made, as in thestructure shown in said patent, for an additional slot corresponding tothe stop signal, because in multiplex transmis sion start and stopsignals are not required.

Fixedly carried on the shaft 31 and disposed between the brackets 38 andas is a worm 40 which controls, through suitable gearing, the propermovement of the perforated tape, as shown in Fig. 12 of said patent andtherein fully described. For purposes of the present disclosure it needonly be mentioned that the size of the gears interconnecting the worm'43and the feed roller for the tape are so calculated as to produce theproper rate of movement of the tape which is caused to move continuouslyto cooperate with the rotating scanning cylinder 26 toeffectsequentially the sensing of the code combinations perforated inthe tape. Rotation is imparted to shaft 31 by its associated synchronousmotor 22-25, which has secured to the armature shaft 43 (Fig. 2) apinion 44 which meshes with a worm gear 45 loosely carried on shaft 31.Gear 45, with its integral hubs, is mounted on the shaft 31 in such amanner as to prevent the longitudinal movement of gear 45 on said shaft.The hub 48 is provided with a single clutch tooth, thus providing apositive clutch which has only one tooth so that the transmitting shaft31 is always picked up in the same phase position. The gear ratiobetween the motor 22 and the shaft I1 is in the present embodiment 1 to1, so that the shaft 31 rotates with the same speed as the motor}! andwill act as though it were an extension of the shaft II of thetransmitting distributor H. Slidably mounted on shaft 31 and cooperatingwith the hub 46 is a sleeve portion 41, which together with the hubportion 48 forms a positive clutch. Sleeve portion 41 is provided with apair of diametrically arranged tongues 4| which fit into a correspondingpair of grooves 49 in a collar 5| fixed to the shaft 31. In this mannera slidable connection is provided between sleeve portion 41 and collar5i. Compressed between a flange 52 integral with the collar 5i and aflange 53 integral with sleeve portion 41 is a compression spring 54.Flange 53 is also provided with a cam portion 55 which cooperates withan arm 56 of an armature lever 51 pivotally mounted at 58 and 59 on abracket 6| carrying a'magnet 62. Armature lever 51 is provided witharmature 63 which cooperates with the cores of the electromagnet 82. Aspring 64 normally draws arm 56 of armature lever I1 toward the collar41. Theextremity of arm 5G is conformed to cooperate with the camportion II, so that when the electromagnet 42 is de-energized, arm 5will be drawn toward the sleeve 41 bringing the end of arm 54 into thepath of the cam portion 55, whereupon, as the sleeve 41 rotatesclockwise (viewing the shaft 81 in the direction of the arrow ii), thecamming relation between cam portion El and the extremity of arm 56 willcause the sleeve 41 to be urged rightwardly against the action pring I4,thereby disengaging the clutch members 40 and 41. Upon energization thecode perforations in the tap due to thefeed but the diflerenceissoslight' as not to be objectionable. It is manifest that the j slopeof the slit 12 would be different for each.

of electromagnet 62 the armature 68 will be attracted, causing thearmature leverlT-to be rotated so as to extend thespring 68, therebydisengaging the end of arm 66 from the cam portion 55, whereupon'spring68 will urge the sleeve 81 leftwardly into engagement with the portion86 of the clutch which rotates with the gear 88, causing rotation of[shaft 81 and consequently initiating rotation of the scanning drum 26.The scanning drum 26 is so located angularly that when the drum 26 is initsstop position (with the clutch disengaged) a blank portion of thedrum periphery corresponding to some other channel of the multiplex willbe presented toward the scanning position. It has been found that mostfavorable results are obtained when the slots or scanning aperture 21are located (with the drum 26 in the stop position) as shown --in Fig.2, so that, when the clutch is re-engaged, the drum 26 will rotate aconsiderable distance, before the scanning apertures 21 come to thescanning position, and will have attained steady motion.

Surrounding the scanning cylinder 26'is a cover member 66, and fixedtoone end of the cover member 66 is an end piece 61 provided with anaperture eccentrically located with respect to the scanning cylinder 26to permit the insertion of the photoelectric cell 28 in as closeproximity to the scanning position as possible. The photoelectric cell28 is suitably mounted in a portion 68 of insulating material which ismounted by screws 68 to the portion 61. Disposedabove the scanningcylinder 26 and arranged over that region thereof embracing thehelically arranged slots 21 is a glass plate 1| which, according to theform of the invention herein shown, comprises an opaquely coatedglasselement in which the slit 12 (Fig. 3) isformed by cutting away a portionof the opaque coating. It may also be advantageous to coat both theupper and lower surfaces of the glass plate 1| and to put correspondingand registrable slits in both surfaces.

Plate ll fits slidably in a groove I8 in the lower side of top plate 88and is held in place by a pair of supp rting guides I8 and I8 (Fig. 3).Plate ll thus is readily removable for cleaning, anddue to the fact thatit is'snugly fitted into plate 85, it serves as a cover plate to closethe chamber containingthe photoelectric cell 28.

The cylindrical cover member 66 is closed at its inner end by a plate"secured to top plate 85,.and it will be understood that the housing forthe scanning drum is light tight, except for the light which passesthrough the slot 12 in the plate II as controlled by the perforatedtape.

' Slit 12 is disposed obliquely and at such an angle as to compensatefor the continuous movement of the tape; that is, due to the obliquelyarranged slit it is possible to transmit a plurality of elementarysignal impulses photoelectrically while the tape is in motion. Thetransmission of signals in any particular channel takes place during aquarter of a revolution of the scanning drum 26 (in a four-channelmultiplex system) while the corresponding tape moves during the entirerevolution of the scanning drum, so that the tape (in such a system)moves substantially four-twentieths of a letter space (assuming a5-1init' code) from the middle of theNo. 1 code impulse to the middle ofthe No. 5 code impulse of the same channel. For this reason, a slope offour-twentieths of ,a letter space gives sumciently accurate timing. Thetiming is, of course, somewhat changed by the unequal spacing ofperforations,

different number of channels of the multiplex system.

The optical apparatus .88 comprises a housing 8| mounted by means ofintegral mem bers 82 and 88 upon top plate 88, and a cap member 88adapted to ,be telescoped into said hous ing. Cap member 88, after beingadjusted telescopically, is locked by means of a lock screw88..Adjustably carried in the cap member '88 is a lamp socket 88 securedto a plate 88, dove tailed for vertical movement into a second plate 81which, in turn, is dovetailed for "horizontal movement into cap .88.Plate 81, after being adjusted, is locked by a lock screw 88, and plate86 is locked after adjustment by a lockscrew 88 (Fig. 5). With thisarrangement, incandescent I 8| and, as indicated in Figs. 2 and 4, isarranged,

so that its longitudinal axis is parallel to and in the same verticalplane as the slot 12.

The tape guiding mechanism associated with the embodiment, of theinvention disclosed herein is as shown .in Figs. 6 and '11 of'theaforementioned patent, and reference may be had to and patent for anunderstanding of the detailed structure of said mechanism. It issufilcient merely to state herein that the tapepasses.

through the tape guideway or track With the transmitting apparatus shownin Fig. 2, 'the three essential elements for performing the scanningfunction; namely, the scanning cylinder, the perforated tape, and thescanning plate, are brought into closest possible prox- 'imity with eachother, and collectively they are arranged close to the optical system orapparatus. In this transmitter, the relative speeds of rotation ,of thetape feed roller andthe scanning cylinder 26 are such that although eachcylinder 28 makes one completerevolution during the interval of time inwhich the tape moves I electric effect.

the distance between two consecutive'rows of perforations, the actualscanning takes place in onequarter revolution. The arrangement, however,is such that each perforation is substantially central with the scanningposition when that perforation is being scanned. With this arrange-.

ment, the time, interval of each signal element is governed by theangular extent of the'slots 21 in the scanning cylinder 26, and due tothe close proidmity of the cylinder 28 tothe scanning plate H the lightflashes upon photoelectric cell 28 will be sharp and distinct to cause asharpturning-on and cutting-off of the photo- .The transmitter showninFig. 2 is initiated into operation by closing the circuit of theautopsynchronous motors l8 and 22-28, thus causing the rotation ofpinion 88 and gear 88. The scanning cylinder 28 and the tape feed rollerare prevented from rotating due to the de-energization of electromagnet82 and the consequent en- Upon energization of magnet 82,-

tape I04 (Fig. 6) is placed in the tape track or guide-way IN and thetape guide member (not shown) is caused to rest thereupon. Contact I82may then be closed to that transmitter. As previously mentioned, atransmitting mechanism such as shown in Fig. 2. is associated with eachof the autosynchronous motors 22, 23, 24, and 25, each one of thetransmitting mechanisms shown in Fig. 2 serving to control thetransmission of messages over a particular channel of a multiplexsystem. According to the present in vention four such channels areprovided, and the reason for arranging the scanning slots 21 in themanner shown in Fig. 9 is so that each tape will be scannedsuccessively, and correspondingly, messages will be transmitted over thechannels of transmission successively.

All of the photoelectric cells 28 are connected in parallel and are alsoconnected to a single amplifying circuit indicated generally as I05(Fig. 1) which is similar to that shown in Fig. of the afore-mentionedpatent. Specifically, in the amplifying system herein disclosed theplate current is reduced to zero in at least two places in a multi-stageamplifier, so that the on" and off" conditions are not affected byvalues of the control light above or below a certain value; that is, theamplifier used with the photoelectric transmitter disclosed herein hastwo stages In the first stage, a certain amount of light cuts oil theplate current, and any additional illumination has no eflect in alteringthe final output of the amplifier, the current in the second stage beingdetermined by the local'adjustment of the circuit. When the light fallsbelow a certain value, sufiicient current flows in the plate circuit ofthe first electronic tube to reduce the current in the plate circuit ofthe second electronic tube to zero, and any further decrease ofillumination has no effect upon the final output.

Having reference to Fig. l, the photoelectric cells 28 are connected inparallel to conductors I06 and I01. As is known, the impingement oflight upon the light sensitive cathode 29 causes the emission ofelectrons therefrom which flow toward the anode or positive electrode 3|of the photo-cell. The cathode 29 is supplied with operating voltagesfrom a source I08, and ordinarily changes in the electron stream flowingwithin the cell, due to varying light intensities falling thereon, willcause varying potential differences to .be set up across a resistanceI09 which is connected in series with the photocell electrodes.

The resistance I09 is also connected in the grid circuit of amulti-electrode electronic tube III having a cathode H2 and acontrolgrid H3. The resistance I08 and the cathode I I2 may be so 7connected to the source I08 as to provide a normal grid biasing sourceH4. The cathode H2 is of the hot cathode type and is heated by a tile.-ment II5 connected to a source of current IIS, for example, thesecondary circuit of a transformer II1. As thus far described, thecircuit comprising source of current I08, photocell 28 (of any one ofthe four transmitting units), and resistance I09 is the source or inputcircuit for the grid control circuit comprising grid H3, cathode II2,conductor II8, biasing source H4, and resistance I09. The plate circuitof electronic tube I II includes the portion of potentiometer source I08included between taps H9 and I2I, conductor II8, cathode II2, plate I22,resistance I23, and conductor I24, and is the source or input circuitfor the grid control circuit of a second electronic tube I25, comprisinga grid I28, cathode I21 and a plate I28. The control circuit for gridI28 includesportion of source I08 included between taps I2I and I29,conductor I24, resistance I23, grid I28, cathode I21, and conductor I3I.The plate circuit of tube I extends from portion of source I08 betweenpoints I29 and I32, conductor I3I, cathode I21, plate I28, thencethrough resistance I33, over conductor I34 to ring I35 of thetransmitting distributor II. It will be observed from Fig. 1, that thereis located in the plate circuit of the last tube I25, a polarized relayI38 having three windings I31, I38, and I39. Therefore, the last tracedcircuit continues from ring I35 over brushes HI and I42 to segmentedring I43 of the distributor II, and thence over conductors I44 or I45,as the case may be, through windings I38 or I39, respectively, of thepolarized relay I35 and back to source I08. Cathode I21 is heated by afilament I46 which, like filament II5, may be connected to the secondaryof transformer H1.

Perforations in the tape I04 (Fig. 7) are indicative of marking signals,and the presentment of a perforation into the scanning region 12 (Fig.3) will permit the impingement of the light beam upon the cathode of thephotocell 28, thereby stimulating the emission of electrons therefromand thus permitting current to flow in said first-mentioned circuit,which is coupled JY means of resistance I09 to the control circuit forgrid H3. The grid H3 is influenced thereby so as to cut off the flow ofelectrons from cathode II2 to plate I22 and thus reduce the platecurrent of the tube III substantially to zero. Cutting oil the platecircuit of tube III, which is the source circuit of the grid controlcircuit of tube I25, renders the grid I26 more positive and increasesthe flow of current in the plate circuit of tube I25 sufliciently toactuate the polarized relay I36 to hold the armature I48 thereof againstcontacts I49 or I 5i as the case may be, depending upon the channel overwhich the signal impulses are transmitted, to impress marking current onthe line wire I52. Winding I31 of the polarized relay I38 is a polarizedwinding and, through rings I53 and I54 of the transmitting distributorII, is connected to the positive terminal for two channels and to thenegative terminal for the remaining two channels. By this arrangementthe normal impulses in some of the channels are made positive and inothers negative so that when all channels are idle, reversals will stillbe transmitted for synchronizing purposes, as is the usual practice.Rings I35 and I43 serve to connect the ampliflers to, one or the otherof the operating windings I38 and I39 (which are reversed), and therelay I35 in response thereto serves to transmit, to the line, impulsescontrolled by all four transmitters of the multiplex system. Theduplexing line relay I55 serves to control the receiving printers I58,I51, I58, and I59 at the transmitting station in response to receivedsignals. The impulses for operating the local printers I59--I59 arederived from the source, I6I, and extend over armature I82 of the relayI55, then over the conductor I83 to the ring I64 of the dissarcastmittedover line wire I52 may beutilized to control through a remote line relayI18 and receiving distributor I 41, the operation of a group oftelegraph printers or recorders I58, for example, of the type disclosedin United States Patent No. 1,665,594, issued to; L. Krum. The. remotelever I98 toward the" clutch portion I84. The extremity or arm I91 isconformed to cooperate with the cam portion on the flange of the clutchportion I94, so that when the electromagnet 282 is de-energized, armI81Iwill be drawn toward the sleeve or clutch portion I84, bringing theend of arm I91 into the path of the cam portion, whereupon, as thesleeve portion I94 rotates in station: indicated by the line relayI18,.is also.

provided with a' transmitting distributor "I for two-way communicationover a duplex line, local printers I58 being also provided thereat.

Modification According to Figs. 9 and 18, a modified form of V theinvention hereinbefore disclosed and embodying the same fundamentalprinciples has been provided. Fig. 9 shows afour-channel photoelectricmultiplex system in which all of the transmitter are driven by directshaft sonnet-- tion from the motor. The arrangement com prises animpulse or synchronous motor I18 as is commonly used in multiplexsynchronous telegraphzsystems. There is also provided a damper I14 of asuitable type to damp out oscillations.

Located at one end of the motor shaft are the commutator rings I15 overwhich pas the brushes I18 driven by the motor I18. 'The commutators I15are substantially-similar to those shown in the transmittingdistributor, shown in Fig. 1. The other end of the motor shaft'is'coupled by means of a coupling I11to the. shaft I18 of a photoelectrictransmitter, indicated generally as I19. The photoelectric transmitterI19 is similar to the transmitter shown in Fig. 2. The shaft I18 of thephotoelectric transmitter I19 is coupled by means of a coupling I8I(similar to coupling I11)" to a shaft l82 of a photoelectrictransmitter, indicated generally as I83; The shaft I82 of thephotoelectric transmitter I88 is coupledby meansgof the coupling I84-toa.

shaft I85 of a' photoelectric transmittenflindicated'genera'lly as I88.Similarly, shaft I85 isconnected by means of a coupling I81 to theshaft,

I88 ofa photoelectrictransmitter I89. Q'lhe motor I13 andthe-photoelectric transmitters I19,

I83, I88 and I89 are mounted as a unit upon a v mentioned Patent No.2,177,877.

Carried onv shafthl18 of the photoelectric transmitter I19, is a singletoothed clutch com-' prising a portion I98 fixed to said shaft and .a

driven portion 194 slidable axially on saidjshaft.

The driven portion I94 13 splined to a pinion I95, and compressedbetween flanges integral with clutch portion I94 and pinion I 85is acompre a sion spring I98. The flange on the clutch por tion I94 isprovided with a camportion (more; clearly shown in the photoelectrictransmitter the direction noted by the arrow, the camming relationbetween cam portion and-the extremity of arm I81 will causetheclutchzportion I84 to be urged leftwardly (as viewed in 9) against theaction of the spring I88, thereby disengaging the clutch membersi98 and184. Conversely,

upon energization of electromagnet 282, the ar mature I98 will beattracted, causing the armature'tobe rotated so as to tension thespring288, thereby disengaging the end of arm "1' from thecam portion,whereupon spring I88 will urge the sleeve of cam'clutch portion I84rightwardly into engagement with the driving portion I88. As previouslymentioned, the pinion I 85 serves to impart movement to the tape movingmecha--' nism, as described in said PatentNo. 2,177,077. Clamped betweenthe pinion I95 and a nut 284 is a scanning cylinder 285, which isprovided with scanning apertures 288 comparable to apertures 21 shown inFig. 2.. A photoelectric cell 281is positioned within the scanningcylinder 28 5, similarly to the mannershown in Fig. 2. I

Photoelectric transmitters I19, I88, I88 and I89 ares1milarlyconstructed, and diifer from each other by the relative positions of theteeth on 'the'driv'ing clutchportions I98 and I94.

Since thearra'n'gement in Fig. 8 is such as'is prov vided for afour-channel multiplex, the teeth288 Y of the grab clutches are spacedninetyrdegrees' apart. 1 Similarly, the series of groups of helical- 1yarrangedscanning apertures 288 are likewise spaced ninety degrees apart;that is, the scanning apertures 288m each of thesoan'ning cylin-e ders285 are spaced one-fourth of a circumference or-90 degrees behind oneanother in the order of transmitters I19,fI88, I88 and I89."

U The arrangement of'the four-channel multiplex system, shown in Fig. 9.is illustrated in' its P' operating position, wherein the magnets 282 ofe ach of the transmitters I18, I88, I88 and I89 are assumed to be" enrgized, thereby permitting the clutch portions of the severalsingletooth. clutches'to'be in operative engagement. j Furthermor, whenall of. the magnets 282 are deenergized, the scanning cylinders 285 willbe stopped or arrested with the'apertures 288 inthe sameposition;namely, that shown in transmit- I ting "distributor I89. In this manner,with the clutchesishown'as described, the scanning cylinders 288 arestopped by the armature of the.'con-.

trol magnet282', so that the solid portion of. the scanning cylindersare opposite the slitsin the glass plates 289, so that no' light willfall on the photoelectric cells 281, and phasing impulses will be c.

tr ic multiplex as will presently appear. Further more, when thescanning cylinders 288 are,

I88) which cooperate with van arm I91 of an armaturelever I98 pivotallymounted at I88 on a bracket 28I carrying an electromagnet 282. A spring288 normally draws arm I81 ofarmature tu're's 2881arrive at. thescanning position so that the scanning drums "Swill-have attdnedsteadymotion. ,7

In Fig. .10 is cult shown in, Fig. 1 may be modified when translucentprinted tape (such as illustrated in transmitted in this quadrant of thephotoelec illustrated new the electrical ch- Fig. 8) is employed as thecontrol strip, thereby reversing the marking and spacing lightconditions on the photoelectric cell; and is similar to the'circuitillustrated in Fig. 1' except that the normal grid bias of theelectronic tube is made more negative, and the photoelectric cell hasbeen connected in such a manner as tables the grid positively when lightfalls upon the photocell. In both of the circuits (Fig. l and Fig. 10)the same eflectis obtained in the tube of the second stage ofamplification; so that marking signals of the same kind. or nature-aretransmitted over the line wire.

It will be remembered that with the circuit shown in Fig. l perforatedtape as shown in-Fig. '7 was employed to control the impingement oflight on the photocell 25, and that a perforation in the tape wasindicative of a marking impulse, so that the presence of light upon thephotocell 25 was likewise indicative of a marking condition. With thecircuit shown in Fig. 10, the contrary is true; that is, the printedspots or areas on the translucent tape shown in Fig. 8 are indicative ofmarking signals, and being imper- -vious to light, prevent the fallingof light upon the photocells 201, so that in this instance the absenceof light upon theiphotocells is indicative of a marking condition. Thecircuit arrangementmay be'such that the plate circuit of the second tubein each case be controlled in the same manner so that the markingsignals transmitted over the line wire are of the same characteristic.To achieve this result, the anodes 2 of the photocells 251 are connectedin parallel to a conductor 2I2', which is connected by a conductor 2 tothe source 2 (analogous to I44, Fig. 1). Cathodes 2l5 or photocells 201are connected in parallel to a common conductor M5, and are supplied.with operating voltages from the source 2 through a resistance 222 and223, whlch, as compared with thenormal grid biasing source I (Fig,. 1)is more negative.. Thus, the grid control circuit of tube 2I3 extendsfrom source 2, through resistance 2I1, over conductor 224, through grid22 I, cathode 2 I 9,

and over conductors 225, 225 and 221 to source 2. The negativeness ofthegrid control circuit just traced is effective, when no light fallsupon the photocell to cut oil the platecurrent of tube 218, the platecircuit of which extends from source 2, over conductors 221, 225 and225, cathode 2I3, plate 223, resistance 223, and conductor 23I toterminal 232 of potentiometer source 2. This plate circuit Just tracedis the source or input circuit'i'or the grid .control circuit of thesecond electronic tube 233, comprisi ing a grid 234, cathode 235 and a'plate 235.

The control circuit for grid 234 includes portion. ofsource 2 l4included between terminals or taps V 232 and 231, conductor23l,1resistance 223, grid m, cathode m, and conductors m and m;

The plate circuit of tube 233 extends from portion of source 214included between taps 231 and 2, through conductors 233 and 235, cathode235, plate 235, thence through resistance 242,

and over conductor 243 to ring 244 of the trans- 'mitting distributorI15. It will be observed from Fig. 10, that there is located in theplate circuit of the last tube 233, a polarized relay 245 having threewindings 245, 241, and 245. There fore, the last traced circuitcontinues from ring 244, over brushes 249 and 25I to segmented. ring 252of the distributor I45, thence over conductors 253 or 254, as the casemay be (as will presently appear), through windings 241 or 248,respectively, of the polarized relay 245, and thence back'to source 2I4.Cathode 235 is heated by a filament 255 which, like filament 224, may beconnected to the secondary of transformer 244.

The current for the exciter lamps 250 may also be derived from thesecondary of transformer 240, or any'other source of current.

Printed areas or spots on the translucent tape (for example, asindicated in Fig. 8) are indicative of marking signal impulses, and thepresentment of a printed area into the scanning region will block orprevent the impingement of the light beam upon the cathode of thephotocell 201. The effect of this condition upon the circuit shown inFig. 10 is to render the grid 22I more negative, which reduces the platecurrent of tube 2I8, which in turn renders the grid 234 of tube 233 morepositive to thus increasethe plate current of the tube 233. It is.therefore, seen that the absence of light on photocell 201 has the sameeffect on tube 233 as the presence of light on photocell 25 (Fig. 1) hadon tube I25. Increasing the flow of current in the plate circuit or tube233 causes the polarized relay 245 to hold its armature 256 againstcontacts 251 or 258 as the case may be, depending upon the channel overwhich the signal impulses are transmitted, to impress marking current onthe line wire 253. Winding 245 of'the polarized relay 245 is a polarizedwinding and, through rings 251 and 262 of the transmitting distributorI15, is connected to the positive terminal for two channels and to thenegative terminal for the remaining two channels. By this arrangement,the normal impulses in some of the channels are made positive and inothers negative so that when all channels are idle, reversals will stillbe transmitted for synchronizing purposes, as is the usual practice.Rings 244 and 252 serve to connect the amplifiers to one or the other ofthe operating windings 241 or 243 (which are reversed), and the relay245 in response thereto serves to transmit, to the line, impulsescontrolled by all four transmitters of the multiplex system. Theduplexing line relay 253 serves to control the receiving printers 254,255, 255 and 251. The impulses for operating the local printers 254251are derived from the source 253, and extend over armature 253 of therelay 253, then over the conductor 21I to the ring 212 of thedistributor I15, then over brushes 213 and 214 to the segmented ring215.

The printers 264 to 251 are connected to the segments of ring 215. Rings215 and 211 supply starting impulses to the printers 254 to 251 in theusual manner. The signals thustransmitted over line wire 25! may beutilized to control, through a remote'line relay 213 and receivingdistributor 282, .the operation of a group of telegraph printers orrecorders 253, for example, of the type disclosed in United StatesPatent No. 1,665,594, issued to H. L. Krum, in the same manner asdescribed in connection with Fig. l. The remote station, indicated bythe line relay 215, is also provided with a transmitting distributor 213for two-way communication over a duplex'line. 1005i messages accordingto the activation of all said printers 283 also being provided thereat.

Although th fipresen't ration r presented 7 connection witlracertairispecific disclosure; {itis contemplated that all forms-whichcome within n e c a m What isclaimed is:- l

1. In a multiplex signaling systi' 1, plurality of photoelectric,transmitters, each transmitter comprising a'cylindrical, scanning devicehavinga helically arrangedseries of slots, one corresponding to eachelement of a code, and meanswhereby each scanning device actsin-succession as a transmitting distributor for the signals controlledby the transmitter of which it forms a part.

2. In a photoelectric signalling system, a plurality of scanningdevices, an independentmotor drive for each scanning device, andautosynchro nous means to maintain a predetermined phase relationbetween the scanning devices.

3. In a signaling system. a plurality of photoelectric cells, acorresponding plurality of cylindrical scanning devices, eachv having ahelically arranged series of apertures embraced in'a predeterminedangular portion thereof, one aperture corresponding to each element of acode to render said devices effective to transmit code signals, andmeans to controlthe transmission of code signals by said scanningdevices sequentially.

4. In a multiplex telegraph system, a plurality of transmittingdistributors, a separate motor to I drive each distributor, andauto'synchronous means to continuously maintain each transmittingdistributor in the correct phase relation to ofphotoelectrictransmitters, each transmitter comprising a scanningdevice, means whereby each scanning device actsas a transmittingdistributor'for the signals cont oiled by the transmitterof which itforms apart, means to arrest any scanning device and means to transmitall spacing signals corresponding to the stopped scanning device. I 7.In a multiplex signalingsystem, a plurality of photoelectrictransmitters, each transmitter comprising a scanning device, meanswhereby, each scanning device acts as a transmitting distributor for thesignals controlled by the transmitter of which it forms a part,meanss'to arrest any scanning device, means to transmit all spacingsignals corresponding to the stopped scanning device, and means totransmit synchronizing signals when all said distributors are stopped.

8. In a multiplex signaling system, a plurality of photoelectric'cells.a correspondingplurality of scanning drums, each drum having a series ofslots, one corresponding to each element of a code, means associatedwith each drum to activate under control of said drum each cellaccording to code signals representing different'messages, an amplifiercommon to all the cells, and distributing m'eans associated with saidamplifier to transmit on a common circuit a plurality of cells. 9. In' amultiplex "signaling system, a plurality of photoelectric'cells; aplurality of corresponding' receivers; and scanning: means comprising aplurality. of? rotaryshutter devices to associate each ,cellinsuccessionin; an operative relation to its corresponding receiver.

10. In a multiplex signaling system, aplurality ofphotosensitivamembers, an exciter lamp associated with eachof saidmembers, rotary shutter means to controlth'eaction oi said'exciter lampon its corresponding member according to a messageto be transmitted, aplurality of recorders, and means operative over a single circuit tocontrol in succession each recorder by its corresponding photosensitivemember. .11. Ina transmitting device. a plurality. of constantlyrotating shafts, a distributing device adapted to be automaticallycoupled to and un-. coupledirom each shaft. and means to couple saiddistributing devices in predetermined relative positions. a

12. In a multiplex telegraph system, a plurality of cylindricaltransmitting distributors, each having a helically arranged series ofslots arranged in quadrature, each slot corresponding to an element of acode, each distributor correspond,- ing to a channel of communication,and meansto simultaneously operate the distributors in such a phaseposition that they are effective in a predetermined sequence to transmitcode-signals under the control ofsaid slots. e v

v 13. In a multiplex telegraph system, a master distributor, aseparately motor driven secondary distributor for each channel. andmeans controlled by the master distributor to operate the secondarydistributors in a predetermined phase relation.

14, In a multiplexphotoelcctric transmitter. aplurality of scanning.drums, each drum carry, ing a series of slots, one corresponding to eachelement of a code, and means to rotate the drums so that the first slotin one drum shall become effective immediately after the last slot inthe immediately preceding drum has become ineffective. g y r 15. ,In amultiplex telegraph system, a'plurality of transmitters, andmeansindependent of.

the transmitters to determine the characterof the marking and spacingimpulses in each of the channels.

16'. In a multiplex telegraph system, a plurality of photoelectrictransmitters. one corresponding to each channel, an amplifier controlledby the transmitters, and means associated with the amplifier to make thecharacter of the spacing and marking inpulses of 7 one rotatablescanning cylin er and each corresponding to an independent messagechannel.

and means autosynchronous to rend er said devices operable in ,such aphase position that they are effective in apredetermined sequence.

18. In a, photoelectric transmitter for synchronous multiplex telegraphsystems, a controlfor'mdof partially light conducting material andhaving thereon groups of code impressions less light conducting than theunimpressed material. means comprising a continuously rotating shutterdevice to photoelectrically scan each group in succession, said devicehaving an opening corresponding to each impulse in a cycle ortransmimion, said impressions being divided into groups representingchannels of the multiplex system with each group corresponding to a setof impulses representing a character signal, and means controlled bysaid -one for each channel of the multiplex, and

means to simultaneously operate the distributors in such a phaseposition that one distributor after another becomes eiiective in apredetermined sequence.

21. In a synchronous multiplex telegraph system, a'plurallty of rotarysignal distributors, one for each channel of the multiplex, means tosimultaneously operate the distributors in such aphase position that onedistributor after another becomes eiiective in a predetermined sequence,and independent signal control means associated with each distributor tocontrol the character oi the transmitted signals.

22. In a telegraph apparatus for the transmission of code signals, arelay, a transmitting switch forming a part of the relay, and meansassociated with the windings of the relay to invert the operation of thetransmitting switch for some of the signals.

23.'In a signaling apparatus, an electronic amplifier, a plurality ofphotoelectric cells,

means comprising a plurality of rotary, shutter devices to operativeiyassociate diflerent photoelectric cells with the amplifier at diiierenttimes, and'a single-toothed clutch device associated with each scanningmeans in such a manner that the several teeth are operativeiy related inpredetermined angular phase, whereby a predetermined phase relation ismaintained between said shutter devices.

24. In a signaling system, an electronic ampliiier, a plurality ofphotoelectric cells, scanning means comprising a plurality of rotaryshutter devices to associate the photoelectric cells with the amplifier,a constantly rotating member, and means to start said shutter devices ina predetermined phase relation to the constantly rotating member.

25. In a photoelectric transmitter for synchronous multiplex telegraphsystems, a control form having thereon groups of light controlling codeimpressions, means comprising a continuously rotating shutter device tophotoelectrically scan each group in succession, said device having anopening corresponding to each impulse in a cycle of transmission, saidimpressions being divided into groups representing channels of themultiplex system with each group corresponding to a set of impulses andrepresenting a character signal, and means controlled by said means tocontrol the signals transmitted over the multiplex system.

26. In a synchronous multiplex telegraph system, a constantlyrotatingdistributor adapted to determine the character of the spacing signal ineach channel of the multiplex, and a signal distributor adapted tochange spacing to marking signals according to signals to betransmitted.

27. In a synchronous multiplextelegraph system, a constantly rotatingdistributor adapted to determine the character of the spacing signal ineach channel of the multiplex, a signal distributor adapted to changespacing to marking signals according to signals to be transmitted, andmeans to stop the second mentioned distributor when no signals are to betransmitted.

28. Ina telegraph system, a transmitting relay, biasing means todetermine the direction of operation of the relay corresponding to aspacing signal, and means to reverse the biasing means for some oi thesignals to be transmitted.

29. In a multiplex synchronous telegraph system, a constantly rotatingmember, a distributor individual to a channel of the multiplex, means toarrest the distributor, and means to start the distributor in apredetermined phase relation to the constantly rotating member.

30. In a signaling system, a plurality of electronic devices eachincluding a cathode, means to increase the electronic mobility of thecathode according to signals to be transmitted and different for eachcathode, and means comprising a plurality of scanning drums wherein eachdrum is provided with a helically arranged series of slots, each slotcorresponding to an element of a code, and means comprising a pluralityof single-toothed clutch devices, wherein the several teeth areoperatively related in predetermined angular phase to render said drumsoperable in such a phase position that they are eiiective in apredetermined sequence to com blue the signals generate-don a singlecircuit.

31. In a photoelectric transmitter for synchronous multiplex telegraphsystems, a control form of light controlling material and having thereongroups of code impressions diflerent in light control than theunimpressed material, means comprising a continuously rotating shutterdevice to photoelectrically scan each group in succession, said devicehaving an opening corresponding to each impulse in a cycle oitransmission, said impressions being divided into groups representingchannels of the multiplex system with each group corresponding to a setof impulses representing a character signal. and means controlled bysaid means to control the signals transmitted over the multiplex system.

32.,In a photoelectric transmitter for synchronous multiplex telegraphsystems, a continuously rotating shutter device having an openingcorresponding to each impulse in a cycle of transmission, said openingsbeing divided into groups representing channels of the multiplexsystemwith each group corresponding to a set of impulses representing acharacter signal, means to illuminate each opening as it passes apredetermined angular position, and means to control the illumination ofeach opening according to impulses to be transmitted over the multiplexsystem.

LOUIS M. PO'I'IS.

